Zucchini is one of the most popular homegrown vegetables, but when things do not go according to plan and you start noticing the leaves of your zucchini plant turning brown, you would want to find a treatment as fast as possible. Your zucchini plant’s leaves can change their color for a variety of reasons. Most of them are diseases, but some are caused by your lack of proper care for your zucchini plant.

Why do zucchini leaves turn brown?

There are many factors that can cause your zucchini leaves from turning brown. Plant diseases are one of them. I will enumerate the kinds of diseases that your zucchini plant could have that cause its leaves to turn yellow. Your negligence can also cause your zucchini leaves to turn brown. The lack of necessary things that it needs in order to thrive can also cause the plant’s leaves to turn brown.

Alternaria Leaf Blight

This is a kind of disease that causes the zucchini leaves to turn yellowish-brown. This starts on the older leaves of your zucchini plant before spreading to the younger leaves. If this disease is not taken care of or left untreated, the fungus will spread throughout the other parts of your zucchini plant and cause your plants to rot and die.

Bacterial Leaf Spot

This bacterial disease begins as a small yellow spot on the leaves of your zucchini plant. And if it isn’t handled, your plant’s leaves will decay and start turning brown. This can also spread to the plant’s fruit.

leaf spot that can cause zucchini leaves from turning brownPin

Bacterial Wilt

This disease causes not only the leaves of your zucchini plant to turn brown but the whole plant to wilt. This disease tends to start with a few leaves that turn dark green to brown for no reason and quickly spread to every part of your zucchini plant.

Overwatering and Underwatering

This is not disease-related but is a lapse on your part in taking care of your zucchini plant. Overwatering your zucchini plant can lead to root rot. And once the roots of your plant are clogged, they will not be able to function properly, and the leaves won’t be able to receive the nutrients that they need to produce food for the plant. And if nothing is done, your plant’s leaves will begin to turn yellow and then eventually becomes brown. On the flip side, underwatering can also inevitably cause the leaves of your zucchini plant to turn brown. The yellowing of your leaves is the first sign of underwatering, and the leaves will eventually turn brown.


Old Age

Any leaves that have reached a certain age will naturally change color. They will start turning yellow to brown and then fall off from your plant. If this occurs in your healthy zucchini plant, there is no need to be alarmed because it is a natural occurrence. There is nothing you can do to change the situation. In fact, it is much better to prune any old leaves yourself instead of waiting for them to fall on their own, as this will allow a new set of leaves to grow in the area where you cut off the old leaves instead of just letting them sit there.

How to treat brown leaves on my zucchini?

  1. Treating a zucchini with Alternaria leaf blight is very easy, trim the infected leaves by cutting them at the base near the stem so that they will not be able to spread. To prevent your plant from having this disease, you will just have to stop watering your zucchini from above and water it at its roots instead. It is advised to cover your zucchini plants during the rainy season.
  1. You can buy disease-resistant varieties of zucchini seeds to prevent your zucchini plant from having bacterial diseases or try rotating your crops every two years. However, if your zucchini plant is already struck by a bacterial disease, it is recommended that you use a copper-based fungicidal spray.
  1. To prevent zucchini bacterial wilt, you need to keep weeds away from your zucchini plants, as they are the most common hosts for cucumber beetle larvae. You can also try laying some dark landscape fabric around your plant to keep the weeds away from them and prevent beetles from laying eggs near your plant. And if your zucchini plant already has this disease, there is nothing you can do but pull up the infected plant and dispose of it to avoid spreading the disease to your other plants.
  1. If you’ve determined that overwatering is causing your plant’s leaves to turn brown, you can just stop giving your plant water for a few days to let the water that is clogging beneath the soil drain. Check your soil to see if the water drains well; the soil also plays a big part in whether your plant’s roots will be clogged with a little water or not. And if you think that your zucchini plant is just underwatered, give it more water than you normally would.

Should you cut dead leaves off zucchini?


It’s a good idea to remove any dead leaves or broken stems from your zucchini plant in the same way you would any other plant. This will encourage new leaf growth in the section you just pruned. The roots will also benefit from the pruning, as they no longer need to provide nutrients to the dead leaves and can focus on other parts of the plant instead.


The cause of your zucchini leaves turning brown is not limited to diseases that they could possibly have; it can also happen if you don’t give your plant the proper care it needs. However, once your plant’s leaves start to change color, you do not need to panic and rush its treatment. It is important to determine the exact cause of why this is happening to your zucchini plant in order to find the appropriate treatment.

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Elizabeth Mcmillan is a passionate gardener with a strong interest in plants. She used to be a teacher, but Elizabeth has spent the last few years immersing herself in the world of plants, learning about their biology and cultural value and trying out different ways of growing them in her own garden. Elizabeth Mcmillan loves indoor plants, succulents, and cacti, and her friends and family know her as a plant care expert.

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